Discharge circuits, devices and methods

ABSTRACT

Discharge circuits, devices and methods. In some embodiments, a MEMS device can include a substrate and an electromechanical assembly implemented on the substrate. The MEMS device can further include a discharge circuit implemented relative to the electromechanical assembly. The discharge circuit can be configured to provide a preferred arcing path during a discharge condition affecting the electromechanical assembly. The MEMS device can be, for example, a switching device, a capacitance device, a gyroscope sensor device, an accelerometer device, a surface acoustic wave (SAW) device, or a bulk acoustic wave (BAW) device. The discharge circuit can include a spark gap assembly having one or more spark gap elements configured to facilitate the preferred arcing path.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.14/685,554 filed Apr. 13, 2015, entitled MEMS DEVICES HAVING DISCHARGECIRCUITS, which claims priority to and the benefit of the filing date ofU.S. Provisional Application No. 61/979,492 filed Apr. 14, 2014,entitled MEMS DEVICES HAVING DISCHARGE CIRCUITS, the benefits of thefiling dates of which are hereby claimed and the disclosures of whichare hereby expressly incorporated by reference herein in their entirety.

BACKGROUND Field

The present disclosure relates to microelectromechanical systems (MEMS)devices having discharge circuits.

Description of the Related Art

Microelectromechanical systems devices, or MEMS devices, typicallyinclude miniaturized mechanical and electro-mechanical elements. SuchMEMS devices can include moving elements controlled by a controller toprovide desired functionalities. MEMS devices are sometimes referred toas microsystems technology devices or micromachined devices.

SUMMARY

According to a number of implementations, the present disclosure relatesto a microelectromechanical systems (MEMS) device that includes asubstrate and an electromechanical assembly implemented on thesubstrate. The MEMS device further includes a discharge circuitimplemented relative to the electromechanical assembly. The dischargecircuit is configured to provide a preferred arcing path during adischarge condition affecting the electromechanical assembly.

In some embodiments, the MEMS device can be a switching device, acapacitance device, a gyroscope sensor device, an accelerometer device,a surface acoustic wave (SAW) device, or a bulk acoustic wave (BAW)device. In some embodiments, the MEMS device can be a switching device.The switching device can be a contact switching device. The dischargecircuit can include a spark gap assembly having one or more spark gapelements configured to facilitate the preferred arcing path. The sparkgap assembly can include a first conductor with one or more spark gapelements and a second conductor with one or more spark gap elements.Each of the one or more spark gap elements of the first and secondconductors can include a shaped conductive feature. The shapedconductive feature can include a sharp feature to increase thelikelihood of arcing. The one or more shaped conductive features of oneof the first and second conductors can be laterally offset from the oneor more shaped conductive features of the other conductor. The lateraloffset of the shaped conductive features of the first and secondconductors can be configured to provide the preferred arcing path as oneconductor moves relative to the other conductor.

In some embodiments, each of the first and second conductors of thespark gap assembly can be located away from the electromechanicalassembly. In some embodiments, one of the first and second conductors ofthe spark gap assembly can be located away from the electromechanicalassembly, and the other conductor can be a part of the electromechanicalassembly. In some embodiments, each of the first and second conductorsof the spark gap assembly can be a part of the electromechanicalassembly.

In some embodiments, the contact switching device can includes a movablefirst electrode and a stationary second electrode as parts of theelectromechanical assembly. The movable first electrode can include abeam having a contact pad. The beam can be configured to be in a firststate in which the contact pad is disengaged from the second electrode,and in a second state in which the contact pad is engaged with thesecond electrode. The contact switch device can further include a gateconfigured to provide an electrostatic force to the beam to therebyallow the beam to be in the first state or the second state. The sparkgap assembly can be configured such that a discharging arc through thepreferred arcing path occurs at a first potential difference between thefirst and second electrodes, with the first potential difference beinglower than a potential difference needed to trigger an arc through thecontact pad when the beam is in the first state. The spark gap assemblycan be further configured so that the first potential difference islower than a lowest potential difference needed to trigger an arcthrough the contact pad in a range of motion of the contact pad relativeto the second electrode. The spark gap assembly can be configured toprovide discharge protection during hot switching operations as well ascold switching operations.

In some embodiments, the contact switching device can include aself-activation functionality, where the self-activation can result froma sufficient voltage difference between the beam and the gate. Theself-activation can result in the contact pad engaging the secondelectrode. The gate can be coupled to ground such that theself-activation results in charge associated with the sufficient voltagedifference between the beam and the gate to be dissipated to the ground.

In some embodiments, the discharge condition can include anelectrostatic discharge (ESD) event. The contact switching device can bean electrostatic discharge (ESD) protection MEMS device. The ESDprotection MEMS device can be configured to have to have either or bothfunctionalities of a faster switching speed and actuation at a lowervoltage than other MEMS devices in a circuit.

In some teachings, the present disclosure relates to a method forfabricating a microelectromechanical systems (MEMS) device. The methodincludes providing a substrate and forming an electromechanical assemblyon the substrate. The method further includes forming a dischargecircuit relative to the electromechanical assembly. The dischargecircuit is configured to provide a preferred arcing path during adischarge condition affecting the electromechanical assembly.

In a number of implementations, the present disclosure relates to aradio-frequency (RF) module that includes a packaging substrateconfigured to receive a plurality of components, and an RF MEMS deviceimplemented on the packaging substrate. The RF MEMS device includes anelectromechanical assembly, and a discharge circuit implemented relativeto the electromechanical assembly. The discharge circuit is configuredto provide a preferred arcing path during a discharge conditionaffecting the electromechanical assembly.

In some embodiments, the RF MEMS device can be, for example, a capacitoror an RF switch. In some embodiments, the RF module can be an antennaswitch module (ASM).

In a number of teachings, the present disclosure relates to a method forfabricating a radio-frequency (RF) module. The method includes providinga packaging substrate configured to receive a plurality of components.The module further includes mounting or forming an RF MEMS device on thepackaging substrate. The RF MEMS device includes an electromechanicalassembly, and a discharge circuit implemented relative to theelectromechanical assembly. The discharge circuit is configured toprovide a preferred arcing path during a discharge condition affectingthe electromechanical assembly.

According to a number of implementations, the present disclosure relatesto a radio-frequency (RF) device that includes a receiver configured toprocess an RF signal, and a front-end module (FEM) in communication withthe receiver. The FEM includes a switching circuit configured to routethe RF signal and having an RF MEMS device. The RF MEMS device includesan electromechanical assembly, and a discharge circuit implementedrelative to the electromechanical assembly. The discharge circuit isconfigured to provide a preferred arcing path during a dischargecondition affecting the electromechanical assembly. The RF devicefurther includes an antenna in communication with the FEM. The antennais configured to receive the RF signal.

In some embodiments, the RF device can be a wireless device such as acellular phone.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGURE shows a block diagram of a microelectromechanical systems (MEMS)device having a discharge circuit.

FIGS. 2A-2C show examples of how a discharge circuit can be implementedrelative to an electromechanical assembly on a MEMS device.

FIG. 3 shows a plan view of an example MEMS contact switch without adischarge circuit.

FIGS. 4A-4C show side views of the switch of FIG. 3 in various stages ofactivation.

FIG. 5 shows a more specific example of the configuration of FIG. 2A,where a discharge circuit can be implemented to be generally separatefrom an electromechanical assembly.

FIGS. 6A and 6B show more specific examples of the configuration of FIG.5.

FIG. 6C shows a sectional view of a discharge circuit of the examples ofFIGS. 6A and 6B.

FIG. 6D shows a more detailed view of a spark gap assembly of thedischarge circuit of FIG. 6C.

FIGS. 7A-C side views of a MEMS device having a discharge circuitintegrated into its electromechanical assembly.

FIG. 8 show a plan view of the MEMS device of FIGS. 7A-7C.

FIG. 9 shows a side view of a MEMS device having a discharge circuitthat is similar to the example of FIGS. 7A-7C, but in which thedischarge circuit is moved further away from a contact pad.

FIG. 10 shows a plan view of the MEMS device of FIG. 9.

FIG. 11 shows a plan view of a MEMS device having a discharge circuitthat is coupled to an electrode but separate from a beam.

FIG. 12 shows a side view of the discharge circuit of FIG. 11.

FIG. 13 shows that in some embodiments, a discharge circuit can includeone or more spark gap elements implemented on a side of a beam, and oneor more spark gap elements implemented on a side of a conductorstructure.

FIG. 14 shows that in some embodiments, a discharge circuit can includea spark gap configuration between two generally fixed parts.

FIG. 15 shows another example in which a discharge circuit can include aspark gap configuration between two generally fixed parts.

FIG. 16 shows a MEMS capacitor having a discharge circuit.

FIG. 17 shows an example of an RF application where MEMS devices havingone or more features as described herein can be implemented.

FIG. 18 shows that in some embodiments, one or more MEMS devices asdescribed herein can be implemented in a module.

FIG. 19 depicts an example wireless device having one or moreadvantageous features as described herein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Disclosed are various examples related to microelectromechanical systems(MEMS) devices and how such devices can include a discharge circuitconfigured to, for example, provide protection against conditions suchas electrostatic discharge (ESD). Although various examples aredescribed in the context of MEMS, it will be understood that one or morefeatures of the present disclosure can also be utilized in otherelectromechanical systems having dimensions larger or smaller (e.g.,NEMS) than typical MEMS dimensions.

FIG. 1 shows a block diagram of a MEMS device 100 having a dischargecircuit 110. In some embodiments, such a discharge circuit can beimplemented substantially within the MEMS boundary and/or volume, and beconfigured to provide an electrical discharge path under certainconditions (e.g., ESD event).

As is generally understood, a MEMS device typically includes anelectromechanical assembly implemented on a substrate. Such anelectromechanical assembly can be configured to yield mechanical changesbased on electrical inputs; and such mechanical changes can yieldchanges in electrical properties of the MEMS device. Contact switchesand capacitors are examples of devices that can be implemented in MEMSform factors. Although various examples are described herein in thecontexts of such switches and capacitors, it will be understood that oneor more features of the present disclosure can also be utilized in otherMEMS devices.

FIGS. 2A-2C show examples of how a discharge circuit 110 can beimplemented relative to an electromechanical assembly 104 on a MEMSdevice 100. FIG. 2A shows that in some embodiments, a MEMS device 100can include an electromechanical assembly 104 implemented on a substrate102. A discharge circuit 110 having one or more features as describedherein can be implemented separately from the electromechanical assembly104. Examples related to such a configuration are described herein ingreater detail.

FIG. 2B shows that in some embodiments, a MEMS device 100 can include anelectromechanical assembly 104 implemented on a substrate 102. Adischarge circuit 110 having one or more features as described hereincan be implemented as a part of the electromechanical assembly 104.Examples related to such a configuration are described herein in greaterdetail.

FIG. 2C shows that in some embodiments, a MEMS device 100 can include anelectromechanical assembly 104 implemented on a substrate 102. Adischarge circuit 110 having one or more features as described hereincan be implemented partially as a part of the electromechanical assembly104, and partially separately from the electromechanical assembly 104.Examples related to such a configuration are described herein in greaterdetail.

In some embodiments, some or all of the different configurations ofFIGS. 2A-2C can be implemented in combination.

As described herein, discharge circuits as described herein can bedesirable in MEMS devices for a number of reasons. For example,protecting MEMS devices and circuits from ESD has been an issue invarious applications. These devices are typically highly sensitive toelectrical overstress, which can cause immediate failures and/or lead tolong term reliability issues. An electrical overstress from ESD eventscan damage, for example, contacts, dielectrics and/or substratesassociated with MEMS devices.

FIG. 3 shows a plan view of an example MEMS contact switch 10 without adischarge circuit, and FIGS. 4A-4C show side views of the switch 10 ofFIG. 3 in various stages of activation. In the example MEMS switch 10, afirst electrode 20 is shown to be implemented as a beam 24 supported ona post 26 which is in turn mounted on a substrate 12 through a base 28.The first electrode 20 is shown to include a contact pad 22 formed at ornear the end opposite from the post 26. When the switch 10 is in an OFFstate (FIG. 4A), the beam 24 can be in its relaxed state such that thecontact pad 22 is separated from a second electrode 30 by a distance d1.When the switch 10 is in an ON state (FIG. 4C), the beam 24 can be inits flexed state such that the contact pad 22 is touching the secondelectrode 30 so as to form an electrical connection between the firstelectrode 20 and the second electrode 30.

In the example MEMS switch 10, transition between the foregoing OFF andON states can be effectuated by a gate 40 configured to provideelectrostatic actuation. For example, when an actuation signal isapplied to the gate 40, the gate 40 can apply an attractiveelectrostatic force (arrow 42) on the beam 24 to thereby pull on thebeam 24. Accordingly, the contact pad 22 of the first electrode 20 movescloser to the second electrode 30 (e.g., in an intermediate stage inFIG. 4B with a gap distance of d2), until the two physically touch toclose the circuit between the first and second electrodes 20, 30. Whenthe actuation signal is removed from the gate 40, the attractive force42 is removed. Accordingly, the beam 24 can return to its relaxed stateof FIG. 4A.

The close proximity of the elements (e.g., the contact pad 22 and thesecond electrode 30 of FIGS. 3 and 4) in a MEMS device can allowelectrical arcing between nearby elements during an ESD event. Such anarcing can damage the MEMS device. For example, contact areas on thecontact pad 22 and the second electrode 30 of the switch 10 arerelatively close to each other, especially during a transition state(e.g., FIG. 4B). Accordingly, arcing can damage such contact areas anddegrade the performance of the switch, or even worse, make the switchun-usable.

FIGS. 5-15 show various examples related to discharge circuitsassociated with MEMS switches. FIGS. 5 and 6 show examples where adischarge circuit can be generally separate from an electromechanicalassembly. FIGS. 7-10 show examples where a discharge circuit can beconsidered to be a part of an electromechanical assembly. FIGS. 11-15show examples where a discharge circuit can be considered to beimplemented partially as a part of an electromechanical assembly andpartially separate from the electromechanical assembly.

Although the examples of FIGS. 5-15 are described in the context ofbeam-type MEMS switches, it will be understood that one or more featuresassociated with the discharge circuits can also be implemented in othertypes of MEMS switches. Further, in the examples of FIGS. 5-15,switching functionality is described in the context of first and secondelectrodes being coupled to input and output (or output and input).However, it will be understood that one or more features associated withthe discharge circuits can also be implemented with other types ofswitching functionalities. For example, a contact pad on a beam cancontact two ends of otherwise separate input and output terminals tothereby close the circuit between the input and output terminals.

FIG. 5 shows a more specific example of the configuration of FIG. 2A,where a discharge circuit 110 can be implemented to be generallyseparate from an electromechanical assembly 104. In FIG. 5, thedischarge circuit 110 of a MEMS device 100 is shown to be implemented ona substrate 102 at a location that is near a portion 106 (of theelectromechanical assembly 104) that is susceptible to ESD events. Inthe context of a beam-type MEMS device 100 of FIGS. 6A and 6B, such aportion susceptible to ESD events can include a contact pad 122 and thecorresponding contact surface on an electrode 130.

In FIGS. 6A and 6B, switching operations between the contact pad 122 ofa first electrode 120 and the second electrode 130 can be achieved inmanners similar to the example of FIGS. 4A-4C. More particularly, thefirst electrode 120 can be implemented as a beam 124 supported on a post126 which is in turn mounted on a substrate 102 through a base 128. Thecontact pad 122 is shown to be positioned at or near the end of the beam124 opposite from the post 126. When the switch 100 is in an OFF state,the beam 124 can be in its relaxed state such that the contact pad 122is separated from the second electrode 130. When the switch 100 is in anON state, the beam 124 can be in its flexed state such that the contactpad 122 is touching the second electrode 130 so as to form an electricalconnection between the first electrode 120 and the second electrode 130.

The foregoing transition between the OFF and ON states can beeffectuated by a gate 140 configured to provide electrostatic actuation.For example, when an actuation signal is applied to the gate 140, thegate 140 can apply an attractive electrostatic force on the beam 124 tothereby pull on the beam 124. Accordingly, the contact pad 122 of thefirst electrode 120 can contact the second electrode 130 to close thecircuit between the first and second electrodes 120, 130. When theactuation signal is removed from the gate 140, the attractive force isremoved so as to result in the beam returning to its relaxed state andthereby separating the contact pad 122 from the second electrode 130 andthereby opening the circuit between the first and second electrodes 120,130.

In FIGS. 6A and 6B, each of the MEMS devices 100 is shown to include adischarge circuit 110 positioned near the contact pad (122) end of thebeam 124. In FIG. 6A, the discharge circuit 110 can be generallyisolated from the electromechanical assembly which includes the firstelectrode 120 and the second electrode 130. Such a configuration can beimplemented if it is desirable to have a discharge such as an ESD berouted to a node other than those connected to the first electrode 120and the second electrode 130. For example, it may be desirable to have adischarge be shunted to ground away from the first and second electrodes120, 130.

In FIG. 6B, the discharge circuit 110 can be coupled to the firstelectrode 120 (through a path 170) and the second electrode 130 (througha path 172), essentially providing a discharge path that is electricallyparallel with the assembly of the first and second electrodes 120, 130.Such a configuration can be implemented if it is desirable to have adischarge path, for an event such as an ESD, bypass sensitive portionsof the first electrode 120 and the second electrode 130. For example, itmay be desirable to have a discharge be routed between the firstelectrode 120 and the second electrode 130, but not through the contactpad 122. As described herein, the discharge circuit 110 can beconfigured to allow such a discharge to occur away from the contact pad122.

As shown in FIGS. 6A-6C, the example discharge circuit 110 can include afirst conductor 150 and a second conductor 160 configured to provide anarcing path that is more preferable than arcing paths between the firstand second electrodes 120, 130. For example, a spark gap configuration182 can be provided where either or both of the first and secondconductors 150, 160 includes one or more shaped conductive features thatlower the potential difference needed to cause arcing.

In the example shown, each conductor (150 or 160) includes a pluralityof sharp conductive protrusions (152 for the first conductor 150, 162for the second conductor 160) that are generally aligned with thecounterpart protrusions of the other conductor (160 or 150). As bettershown in FIG. 6D, design parameters such as dimensions of the sharpprotrusions (152, 162), gap distance (z) between two counterpartprotrusions, and spacing (x) between the neighboring protrusions can beselected to provide desired arcing properties.

As shown in FIG. 6C, the foregoing spark gap configuration 182 can beimplemented by positioning the first conductor 150 at a distance fromthe second conductor 160. If the second conductor 160 is positioned onthe substrate 102, the first conductor 150 can be positioned in such amanner by posts 156 and their respective bases 158.

The discharge circuit 110 configured in the foregoing manner can providea structure that results in arcing at lower potential difference levelsthan that of the electromechanical assembly so that the charge of an ESDevent can be dissipated appropriately with little or no damage to theelectromechanical assembly. Design of the spark gap configuration 182 inFIGS. 6A-6C can be relatively easier due to the static nature of thedischarge circuit 110 where the protrusions 152, 162 of the first andsecond conductors 150, 160 generally do not move relative to each other.Accordingly, one set of protrusions (152 or 162) can remain at a fixedposition relative to the other set of protrusions (162 or 152). Forexample, the sharp points of the protrusions 152 can be positioned andremain substantially aligned with the sharp points of the protrusions162.

In some embodiments, some or all of a discharge circuit can beintegrated into an electromechanical assembly. For example, FIGS. 7A-Cand 8 show side and plan views of a MEMS device 100 having a dischargecircuit 110 integrated into its electromechanical assembly 104. Thedischarge circuit 110 is shown to include a spark gap configurationbetween one or more shaped conductive features 190 on an underside of afirst electrode 120 and one or more shaped conductive features 192 on anupper side of a second electrode 130. The conductive features 190, 192are shown to be positioned so as to provide one or more arcing paths atlocation(s) away from the switching contact area (e.g., between acontact pad 122 and the corresponding area on the second electrode 130).Accordingly, in an ESD event, such an arcing through the spark gap canprevent or reduce damage to the switching contact area.

In the example of FIGS. 7 and 8, the configuration of the first andsecond electrodes 120, 130 can be similar to those of FIGS. 6A and 6Band FIGS. 3 and 4, other than the presence of the integrated dischargecircuit 119 in FIGS. 7 and 8. Accordingly, switching operations actuatedby a gate 140 can be performed in similar manners.

In the example discharge circuit 110 of FIGS. 6A-6D, the spark gapconfiguration includes the spark gap elements (e.g., shaped conductorfeatures) arranged in a fixed manner (e.g., with the sharp tipsaligned). In the example of FIGS. 7 and 8, however, relative position ofthe spark elements (190 for the first electrode 120, and 192 for thesecond electrode 130) does not remain constant during a switchingoperation due to the movement of the beam 124. Accordingly, in someembodiments, the spark elements 190, 192 can be arranged so as toprovide a preferred arcing path during some or all of the entiremovement range of the beam 124 without making physical contact.

In some embodiments, and as shown in FIGS. 7 and 8, the foregoingarrangement of the spark gap elements 190, 192 can be achieved byproviding a lateral offset between the upper spark gap elements 190 andthe lower spark gap elements 192. Such an arrangement can allow the beam124 to move in its full range of motion while providing desireddistances between the spark gap elements 190, 192 without physicalcontact. Such a spark gap configuration can provide a preferred arcingpath over an arcing path involving the contact pad 122 during some orall of the entire movement range of the beam 124.

The foregoing configuration (where arcing is more likely through thepreferred arcing path) can be particularly useful for providingdischarge protection during hot switching operations. In a hot switchingoperation, a signal being switched ON or OFF is present on one of theelectrodes. When the contact pad 122 is closer to the second electrode130 (e.g., FIG. 7B when it moves towards the second electrode 130 toclose the switch, or when it moves away from the second electrode uponopening of the switch), arcing is more likely due to the smaller gap.Without the discharge circuit 110, arcing resulting from the signalitself can occur; and such arcing during hot switching operation canresult in damage to the contact pad 122 and/or the second electrode 130.As described herein, the discharge circuit 110 can be configured toprovide a preferred arcing path, even when the contact pad 122 is veryclose to the second electrode 130.

FIGS. 9 and 10 show side and plan views of a MEMS device 100 having adischarge circuit 110 that is similar to the example of FIGS. 7 and 8.However, in the MEMS device 100 of FIGS. 9 and 10, the discharge circuit110 is shown to be moved further away from the contact pad 122 and onthe other side of the gate 140. To accommodate such a configuration, aconductor structure 204 can be provided to include one or more lowerspark gap elements 202 (e.g., shaped conductive features). Such lowerspark gap elements are shown to be arranged in a laterally offset mannerrelative to one or more upper spark gap elements 200 (e.g., shapedconductive features) formed on the underside of the beam 124, toaccommodate the movement of the beam 124.

Similar to the example of FIGS. 7 and 8, the foregoing spark gap betweenthe upper and lower spark gap elements 200, 202 can provide a preferredarcing path in hot or cold switching operations. The discharge circuit110 of FIGS. 9 and 10 being further away from the contact pad 122 can beuseful in, for example, applications where a signal is present in thefirst electrode 120 and where arcing during hot switching operation is aconcern. The closer proximity of the discharge circuit 110 to the sourceof the signal (e.g., the base 128), combined with its spark gapconfiguration providing a preferred arcing path, can make it more likelythat arcing due to the signal itself will be routed through thedischarge circuit 110.

In some embodiments, and as shown in FIG. 10, the lower spark gapelements 202 are shown to be electrically connected to the secondelectrode 130 through the conductor structure 204 and a conductive path206. Accordingly, the discharge circuit 110 can be considered to providea parallel and more preferred arcing path than an arcing path involvingthe contact pad 122. As described herein, the discharge circuit 110 canbe connected in other manners to provide different routing options. Forexample, the lower spark gap elements 202 can be connected to ground.

FIG. 11 shows a plan view of a MEMS device 100 having a dischargecircuit 110 that is coupled to the first electrode 120 but separate fromthe beam 124. FIG. 12 shows a side view of the discharge circuit 110.

In FIGS. 11 and 12, the electromechanical assembly 104 can be configuredfor switching operations in similar manners as the other beam-actuatedswitch examples described herein. The discharge circuit 110 is shown toinclude a spark gap configuration between one or more upper spark gapelements 212 (e.g., shaped conductive features) and one or more lowerspark gap elements 222 (e.g., shaped conductive features). The upperspark gap elements 212 can be formed on the underside of a conductor 210supported by posts 214, 216. The post 216 is shown to be connected tothe base 128 of the electromechanical assembly 104. The lower sparkelements 222 can be formed on the upper surface of a conductor structure220. Since the spark gap elements 212, 222 generally do not move, theycan be positioned relative to each other to provide a desired arcingproperty.

In the example of FIGS. 11 and 12, the lower spark gap elements 222 areshown to be electrically connected to the second electrode 130 throughthe conductive structure 220 and a conductive path 224. Accordingly, thedischarge circuit 110 can be considered to provide a parallel and morepreferred arcing path than an arcing path involving the contact pad 122.As described herein, the discharge circuit 110 can be connected in othermanners to provide different routing options. For example, the lowerspark gap elements 222 can be connected to ground.

The example of FIGS. 11 and 12 can provide similar dischargefunctionality as the example of FIG. 6, utilizing a fixed spark gapconfiguration. In the example of FIGS. 11 and 12, the discharge circuit110 being further away from the contact pad 122 and being coupled moredirectly to the first electrode 120 can be advantageous in applicationswhere a signal is input through the first electrode 120. The dischargecircuit 110 can be configured to provide discharge protection in hot orcold switching operations. For the hot switching operation, the sparkgap between the elements 212, 222 can be configured appropriately toprovide a preferred arcing path for some or all of the movement range ofthe contact pad 122.

In the various examples described in reference to FIGS. 6-12, the sparkgap configurations include spark gap elements that form vertical gapssimilar to the vertical arrangement of the first and second electrodes.Other configurations of spark gaps can also be implemented.

For example, FIGS. 13-15 show discharge circuits 110 having lateralspark gap configurations. In each of the examples of FIGS. 13-15, theelectromechanical assembly 104 can be configured for switchingoperations in similar manners as the other beam-actuated switch examplesdescribed herein.

In the example of FIG. 13, the discharge circuit 110 is shown to includea spark gap configuration between one or more spark gap elements 230(e.g., shaped conductive features) on a side of the beam 124 and one ormore spark gap elements 232 (e.g., shaped conductive features) on a sideof a conductor structure 234. In such a configuration, either or both ofthe spark gap elements 230, 232 can be configured to accommodate themovements of the beam during switching operations so as to provide apreferred arcing path over an arcing path involving the contact pad, forsome or all of the movement range.

In the example of FIG. 13, the spark gap elements 232 are shown to beelectrically connected to the second electrode 130 through theconductive structure 234 and a conductive path 236. Accordingly, thedischarge circuit 110 can be considered to provide a parallel and morepreferred arcing path than the arcing path involving the contact pad122. As described herein, the discharge circuit 110 can be connected inother manners to provide different routing options. For example, thespark gap elements 232 can be connected to ground.

In some applications, it may be desirable to have opposing spark gapelements remain generally fixed relative to each other during movementsof the beam of an electromechanical assembly 104. In such aconfiguration, the spark gap elements can remain generally fixed duringthe movements of the beam. Accordingly, the spark gap elements can beconfigured to provide a preferred arcing path over an arcing pathinvolving the contact pad, for some or all of the movement range of thebeam. FIGS. 14 and 15 show non-limiting examples of such aconfiguration.

In the example of FIG. 14, the discharge circuit 110 includes a sparkgap configuration between two generally fixed parts. For example, thespark gap configuration of the discharge circuit 110 is shown to bebetween one or more spark gap elements 240 (e.g., shaped conductivefeatures) on a side of a base 128 of the first electrode 120 and one ormore spark gap elements 242 (e.g., shaped conductive features) on a sideof a conductor structure 244. A conductor structure 248 can beimplemented on the base 128 to elevate the spark gap elements 240 to alevel appropriate for the spark gap elements 242.

In the example of FIG. 14, the spark gap elements 242 are shown to beelectrically connected to the second electrode 130 through theconductive structure 244 and a conductive path 246. Accordingly, thedischarge circuit 110 can be considered to provide a parallel and morepreferred arcing path than the arcing path involving the contact pad122. As described herein, the discharge circuit 110 can be connected inother manners to provide different routing options. For example, thespark gap elements 242 can be connected to ground.

In the example of FIG. 15, the discharge circuit 110 is similar to theexample of FIG. 14, in that the spark gap configuration is between twogenerally fixed parts. For example, the spark gap configuration of thedischarge circuit 110 is shown to be between one or more spark gapelements 250 (e.g., shaped conductive features) and one or more sparkgap elements 252 (e.g., shaped conductive features). In someembodiments, such spark gap elements can be implemented on or near thesurface of the substrate 102, on one or more conductor structures toelevate the spark gap elements from the substrate 102, or anycombination thereof.

In the context of the spark gap elements 250, 252 being on conductorstructures, the spark gap elements 250 can be implemented on a side of aconductor structure 258, and the spark gap elements 252 can beimplemented on a side of a conductor structure 254. In some embodiments,some or all of the conductor structure 258 can be provided by a post 126that supports a beam 124 of the first electrode 120. The conductorstructure 254 can be formed underneath the beam 124 and adjacent thepost 126 so as to allow the spark gap elements 252 to be positionedappropriately relative to the spark gap elements 250.

In such a configuration, the spark gap elements 250, 252 can remaingenerally fixed during the movements of the beam 124. Accordingly, sparkgap elements 250, 252 can be configured to provide a preferred arcingpath over an arcing path involving the contact pad 122, for some or allof the movement range of the beam 124.

In the example of FIG. 15, the spark gap elements 252 are shown to beelectrically connected to the second electrode 130 through theconductive structure 254 and a conductive path 256. Accordingly, thedischarge circuit 110 can be considered to provide a parallel and morepreferred arcing path than the arcing path involving the contact pad122. As described herein, the discharge circuit 110 can be connected inother manners to provide different routing options. For example, thespark gap elements 252 can be connected to ground.

Based on the various examples described herein, one can see that adischarge circuit can be implemented in a MEMS device so as to provide apreferred arcing path from any conductive feature associated with thefirst and/or second electrodes of an electromechanical assembly.Accordingly, such variations are contemplated in the present disclosure.

As also described herein, a discharge circuit can be implemented in aMEMS device by way of one or more conductive features that are separatefrom the first and/or second electrodes of an electromechanicalassembly. Such conductive feature(s) of the discharge circuit may or maynot be electrically coupled to the first and/or second electrodes.Accordingly, variations involving such configurations are contemplatedin the present disclosure.

As also described herein, a discharge circuit can be based on one ormore conductive features associated with an electromechanical assemblyand one or more conductive features generally separate from theelectromechanical assembly. Accordingly, variations involving suchconfigurations are contemplated in the present disclosure.

In the various examples described herein, various spark gapconfigurations are described in the context of an air gap, and atlocations above a substrate. However, it will be understood that sparkgaps having one or more features as described herein can also beimplemented such that some or all of the spark gap elements are within,for example, a substrate, a dielectric material, or any other materialthat provides electrical isolation between the elements.

In the various examples disclosed herein, various spark gapconfigurations are describe in the context of being implemented atvarious locations relative to an electromechanical assembly. It will beunderstood that a MEMS device can include more than one of such sparkgaps at different locations to provide even more robust dischargeprotection for the MEMS device.

As described herein, at least some of the spark gap configurations ofthe various discharge circuits can be suitable for providing dischargeprotection during hot switching operations. Such a feature can beparticularly advantageous, especially when one considers typicallifetime expectancies associated with hot-switching (e.g., about 100million cycles) and cold-switching (e.g., about 5 billion cycles)operations.

In the various examples of FIGS. 3-15, the MEMS devices are described inthe context of switching devices. It will be understood that other typesof MEMS devices can also include a discharge circuit having or morefeatures as described herein.

For example, FIG. 16 shows a MEMS capacitor 100 having a dischargecircuit 110. In the example of FIG. 16, the MEMS capacitor 100 is shownto be similar to the switch example of FIGS. 9 and 10. A dielectriclayer 260 is shown to be formed on the surface of a contact pad 122 of afirst electrode 120. Similarly, a dielectric layer 262 is shown to beformed on the surface of a second electrode 130. Accordingly, when thebeam is in its relaxed state (e.g., as in FIG. 16), a first capacitanceexists between the first and second electrodes 120, 130. When the beamis in its flexed state due to the actuation by the gate 140, thedielectric layer 260 of the contact pad 122 comes into physical contactwith the dielectric layer 262 of the second electrode 130 (but not inelectrical contact) thereby yielding a second capacitance that istypically greater than the first capacitance. Values of the first andsecond capacitances can be adjusted by, for example, materials and/orthicknesses of the dielectrics 260, 262, and the separation gap when inthe relaxed state.

In the example of FIG. 16, the discharge circuit 110 is shown to includeone or more spark gap elements 270 (e.g., shaped conductive features)formed on the underside of the beam 124, and one or more spark gapelements 272 (e.g., shaped conductive features) formed on an uppersurface of a conductor structure. The spark gap elements 270, 272 may ormay not be completely covered by their respective dielectrics.

In some embodiments, the spark gap elements 270, 272 can be configuredto add little or minimized capacitance between the elements, so as tonot impact the capacitances associated with the first and secondelectrodes 120, 130. In some embodiments, the spark gap elements 270,272 can be configured to contribute to the overall capacitances of theMEMS device in some desirable manner. In the context of switchingdevices as described herein, the spark gap elements can be configured toadd little or minimized capacitance between the elements, so as toreduce or minimize parasitic capacitances associated with the switches.

In the example of FIG. 16, the spark gap elements 270, 272 are shown tobe configured in a laterally offset manner similar to the example ofFIGS. 9 and 10. Accordingly, the MEMS capacitor 100 can be switchedbetween the two capacitance states while “hot,” and have the dischargecircuit 110 provide a preferred arcing path throughout such transitions.

It will be understood that MEMS capacitors can also be implemented withdifferent discharge circuit configurations, including those examplesdescribed herein.

It will also be understood that, although various examples are describedherein in the contexts of contact MEMS devices (such as contactswitches) and capacitive MEMS devices, one or more features of thepresent disclosure can also be implemented in other MEMS applicationsand/or applications involving electromechanical devices. Suchapplications and/or devices can include, but are not limited to,gyroscopes, accelerometers, surface acoustic wave (SAW) devices, bulkacoustic wave (BAW) devices, and any other MEMS devices that aresensitive to ESD events and/or hot switching problems. In the context ofcontact switches, other RF and/or non-RF applications can include, forexample, load switches in power supplies, voltage converters andregulators (e.g., where MEMS switches can replace FET switches); andpower switches such as those configured to handle high power and/or highvoltage (e.g., low frequency) signals.

MEMS devices having one or more features as described herein can beutilized in a number of electronic applications, includingradio-frequency (RF) applications. In the context of RF applications,electrostatically-actuated MEMS devices, such as the MEMS switches andMEMS capacitors as described herein, can provide desirablecharacteristics such as low insertion loss, high isolation, highlinearity, high power handling capability, and/or high Q factor.

FIG. 17 shows an example of an RF application where MEMS devices havingone or more features as described herein can be implemented. The exampleof FIG. 17 includes a multiple port switching configuration involving RFPort 1, RF Port 2 and RF Port 3. RF Port 1 can be, for example, a commonantenna port, and RF Ports 1 and 2 can be associated with, for example,first and second RF band signal paths. In such an example context, therecan be more than two RF bands coupled to the common antenna port.

Each of the three ports is shown to be coupled to a switchable shuntpath to ground. For RF Port 1, the shunt path can include an ESDprotected MEMS switch. For RF Port 2, the shunt path can include an ESDprotected MEMS switch. For RF Port 3, the shunt path can include an ESDprotected MEMS switch. In some embodiments, each of such ESD protectedMEMS switch can be configured as a self-actuating MEMS switch.Additional details concerning such self-actuating MEMS switches aredescribed herein in greater detail.

In FIG. 17, a MEMS switch (Port 1 MEMS) can be provided between thesecond port (RF Port 2) and a common node shared by the three ports.Similarly, a MEMS switch (Port 2 MEMS) can be provided between the thirdport (RF Port 3) and the common node. Such MEMS switches (Port 1 MEMSand Port 2 MEMS) are shown to have their gates controlled by a switchgate controller.

In some embodiments, some or all of the foregoing MEMS devices (RF Port1 ESD Protection MEMS, RF Port 2 ESD Protection MEMS, RF Port 3 ESDProtection MEMS, Port 1 MEMS, Port 2 MEMS) can include respectivedischarge circuits having one or more features as described herein. Inthe context of the self-actuating MEMS switches (e.g., RF Port 1 ESDProtection MEMS, RF Port 2 ESD Protection MEMS, RF Port 3 ESD ProtectionMEMS), spark gaps of their respective discharge circuits can beconfigured to facilitate and/or improve the self-actuating process.

With respect to self-actuation, it is noted that MEMS devices canself-actuate under certain conditions (e.g., higher voltage conditions).Such a property can be undesirable under some operating conditions;however, the same property can be utilized in other operating conditionsto provide, for example, a switchable path to ground during ESD events.

In MEMS RF switch devices, such self-actuation can occur inbeam-actuated configurations in which a beam is actuated by applying avoltage to the gate to thereby create an electrostatic force on thebeam. In such a configuration, a beam can self-actuate, without theforce from the gate, if there is a sufficient voltage difference betweenthe beam and the gate.

During a typical ESD event, very high voltages can be applied to a MEMSdevice. In a MEMS device where the gate and one electrode are grounded,and the other electrode is located on the beam, such a high voltageassociated with ESD can allow the beam to self-actuate and close thecircuit between the two electrodes. This self-actuation allows theenergy associated with the ESD event to be discharged to ground beforeother elements of the device are harmed. As described herein, use ofdischarge circuits in such self-actuated MEMS switches can allow the ESDProtection MEMS devices to be designed to actuate at a lower voltageand/or to have faster switching speeds.

In the example of FIG. 17, suppose there is an ESD event across any twoports. Such an ESD event will likely yield a large voltage differentialbetween the beam and the gate of some or all of the ESD Protection MEMSdevices. The affected ESD Protection MEMS device can have its beamself-actuated by the voltage differential; and since the affected gateis grounded, the ESD energy can safely dissipate to ground before damageoccurs. Again, use of discharge circuits can allow such ESD ProtectionMEMS devices to be designed to actuate at a lower voltage and/or to havefaster switching speeds to, for example, provide better protection ofthe rest of the devices (e.g., by activating before the rest of thedevice and thereby handling the discharge).

As disclosed herein, ESD Protection MEMS devices can be implemented asMEMS switches; and such MEMS switches may or may not includeself-actuation functionality. As also disclosed herein, a dischargecircuit having one or more features as described herein can beimplemented in any of such MEMS devices, including but not limited to, aMEMS device (e.g., a switch) which may or may not be specificallyconfigured to provide ESD protection, and a MEMS switch with or withoutself-actuation functionality.

FIG. 18 shows that in some embodiments, one or more MEMS devices asdescribed herein can be implemented in a module 300. The example module300 can include a packaging substrate 302 configured to receive aplurality of components. At least some of such components can includeone or more MEMS devices 100; and some or all of such MEMS devices caninclude a discharge circuit 110 having one or more features as describedherein.

In the example of FIG. 18, five of such MEMS devices 100 are shown to beimplemented on the substrate 302 and connected between three exampleports to provide switching functionalities similar to the example ofFIG. 17. In the example of FIG. 18, the antenna port (ANT) can be thefirst port (Port 1) of FIG. 17; and the ports for Band 1 and Band 2 canbe the second and third ports (Port 2, Port 3) of FIG. 17. The five MEMSdevices 100 can be mounted or formed on the substrate 302, and suchdevices can be interconnected to provide desired functionalities. In theexample of FIG. 18, a switch controller component 304 is also depictedas being on the module 300. Other components can also be implemented onthe module 300.

In some embodiments, the module 300 can be an antenna switching module(ASM). In some embodiments, the module 300 can be a front-end module(FEM) in which case other components such as power amplifiers, low-noiseamplifiers, matching circuits, and/or duplexers/filters can be included.

In some implementations, an architecture, device and/or circuit havingone or more features described herein can be included in an RF devicesuch as a wireless device. Such an architecture, device and/or circuitcan be implemented directly in the wireless device, in one or moremodular forms as described herein, or in some combination thereof. Insome embodiments, such a wireless device can include, for example, acellular phone, a smart-phone, a hand-held wireless device with orwithout phone functionality, a wireless tablet, a wireless router, awireless access point, a wireless base station, etc. Although describedin the context of wireless devices, it will be understood that one ormore features of the present disclosure can also be implemented in otherRF systems such as base stations.

FIG. 19 depicts an example wireless device 400 having one or moreadvantageous features described herein. In some embodiments, suchadvantageous features can be implemented in a module 300 such as anantenna switch module (ASM). In some embodiments, such a module caninclude more or less components than as indicated by the dashed box.

Power amplifiers (PAs) (collectively depicted as 412) (e.g., in a PAmodule) can receive their respective RF signals from a transceiver 410that can be configured and operated to generate RF signals to beamplified and transmitted, and to process received signals. Thetransceiver 410 is shown to interact with a baseband sub-system 408 thatis configured to provide conversion between data and/or voice signalssuitable for a user and RF signals suitable for the transceiver 410. Thetransceiver 410 is also shown to be connected to a power managementcomponent 406 that is configured to manage power for the operation ofthe wireless device 400. Such power management can also controloperations of the baseband sub-system 408 and other components of thewireless device 400.

The baseband sub-system 408 is shown to be connected to a user interface402 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 408 can also beconnected to a memory 404 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

In the example wireless device 400, the module 300 can include one ormore MEMS devices configured to provide one or more desirablefunctionalities as described herein. Such MEMS devices can facilitate,for example, operation of the antenna switch module (ASM) 414 in adischarge-protected manner. In some embodiments, at least some of thesignals received through an antenna 420 can be routed from the ASM 414to one or more low-noise amplifiers (LNAs) 418. Amplified signals fromthe LNAs 418 are shown to be routed to the transceiver 410.

A number of other wireless device configurations can utilize one or morefeatures described herein. For example, a wireless device does not needto be a multi-band device. In another example, a wireless device caninclude additional antennas such as diversity antenna, and additionalconnectivity features such as Wi-Fi, Bluetooth, and GPS.

In the various examples disclosed herein, discharge circuits aredescribed as being configured to provide preferred discharge paths byway of, for example, arcing across opposing spark gap elements. It willbe understood that use the term arcing or arc can include anytransmission of energy such as electrical energy between two or moreelectrically non-contacting elements. Such transmission of energy can bedue to, for example, ionization, and/or conduction; and can be through,for example, gas (including air), semiconductor, electrical insulator,and/or dielectric.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A microelectromechanical systems (MEMS) devicecomprising: a substrate; an electromechanical assembly implemented onthe substrate; and a discharge circuit implemented relative to theelectromechanical assembly, the discharge circuit configured to providea preferred arcing path during a discharge condition affecting theelectromechanical assembly.